1. Introduction
This manual describes the operation of the Kaelus Range-to-Fault (RTF) system. This system enables the user to
pinpoint the locations and magnitudes of PIM and Return Loss faults in RF infrastructure of the type typically found in
cellular mobile telephone base stations.
The RTF system comprises an external device called an RTF module connected to a suitably equipped iQA or iPA
portable PIM analyzer. Customers can purchase an RTF-ready PIM analyzer from Kaelus, or can arrange a factory
upgrade to their existing iQA to become RTF compatible.
2. Functional Description
2.1 Passive Intermodulation Distortion
Passive intermodulation distortion (PIM) is a form of electromagnetic interference that is often encountered in full-duplex
radio communications systems such as cellular mobile telephone networks. Its root causes and eects on network
performance are described in detail in the iQA/iPA Operating Manuals, but suce it to say that PIM is an extremely
undesirable phenomenon that is of increasing concern to cellular network operators.
2.2 Conventional PIM Testing Equipment
In response to the challenges presented by PIM, a new family of test instruments has come onto the market in recent
years. Commonly referred to as “PIM analyzers”, these instruments measure the overall PIM performance of the RF
infrastructure using the method of Test Setup 1 of IEC62037. The iQA/iPA portable PIM analyzer from Kaelus is one
example of this type of instrument.
While useful in determining whether or not a system has a PIM problem, conventional PIM analyzers do not provide
any information about the locations of PIM faults in the device under test. Consequently, PIM faults can still be labor-
intensive and time-consuming to resolve, especially in complex systems containing many RF cables, components and
interconnects.
2.3 RTF Module
The lack of detailed information about where PIM faults are located has previously been a key limitation of conventional
PIM analyzers. However, this shortcoming has now been remedied with the development of the Kaelus RTF module.
When attached to an iQA/iPA portable PIM analyzer, the RTF module enables the iQA/iPA to determine the location and
magnitude of individual PIM faults in the RF infrastructure.
In addition to this, the RTF module enables the iQA/iPA to pinpoint the location and magnitude of individual Return Loss
faults in the RF infrastructure.
2.4 Measurement Process
2.4.1 PIM vs Distance
The RTF system measures the distance to PIM faults by performing a frequency-swept reected PIM measurement in
accordance with Test Setup 1 of IEC62037.
At each point in the sweep, the iQA/iPA generates two high-power synthesized carriers in the transmit band of the
instrument. These carriers are emitted from the test port and propagate into the device under test, where PIM is
generated by the faulty components and interconnects therein. The resulting 3rd or 5th order intermodulation product is
automatically calculated, and the RTF module’s receiver is tuned to the required frequency. The RTF module measures
the amplitude of the PIM product, and also its phase relative to a local reference tone. This process is repeated at every
point in the frequency sweep. Upon completion of the sweep, the measured results are post-processed by the iQA/iPA,
and the PIM fault locations and amplitudes are displayed on the screen.
Operating Manual | Passive Intermodulation and Return Loss Fault Ranging Device
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